I just found out something ( to anyone that doesn't know it yet ).
I took out my bottom plate on my mbp the other day to change the ram, when i put it back together it's not as flush as it was in the beginning ( doesn't fit properly, the edges are abit off )
The reason was i thought all the small screws were the same but they weren't. Theres actually 4 screws that goes in the bottom that are different, i can't really describe how they are but they are
the length are the same but there is a difference between them, just look closely 
I took out my bottom plate on my mbp the other day to change the ram, when i put it back together it's not as flush as it was in the beginning ( doesn't fit properly, the edges are abit off )
The reason was i thought all the small screws were the same but they weren't. Theres actually 4 screws that goes in the bottom that are different, i can't really describe how they are but they are